Polymer materials compatible with biological environments are of high interest due to their potential for use in a range of biomedical applications, such as tissue engineering. Polymer materials that have been investigated for use in such applications are generally of synthetic or natural origin.
Natural polymer materials such as collagen, alginate, chitosan and hydroxyapatite have been utilised in the preparation of scaffolds for tissue engineering applications targeting a variety of tissues. While such natural materials have many advantages, there are certain issues in regards to their use, such as batch-to-batch variation, risk of disease transmission and immunogenicity. In addition, processing methods required to obtain these natural materials can affect their physical properties. For example, even though collagen demonstrates high mechanical strength in vivo, the process of harvesting, isolation and purification significantly degrades this property due to the loss of natural cross-links.
Synthetic polymers on the other hand offer certain advantages over natural polymers. Such advantages can include a reduction in batch-to-batch variation, a higher degree of control over polymer structure, and the ability to tailor polymer composition and properties to suit particular applications.
Hydrophilic materials based on polyether polymers such as poly(ethylene glycol) (PEG) have been explored for biomedical applications. PEG in particular has been widely studied due to its water solubility, non-toxicity, minimal immunogenicity and anti-protein fouling properties, and has been approved by the US Food and Drug Administration (FDA) for use in drug and cosmetic applications. Various studies, in vitro and in vivo, have demonstrated the desirable biocompatibility of materials fabricated with PEG.
Crosslinked polymer network polymers and hydrogels based on polyethers such as PEG have been investigated for cell culture and tissue engineering applications, and various research groups have reported on the construction of PEG hydrogels using a variety of reaction conditions. However, while the PEG polymers and hydrogels are generally biocompatible, they are often not biodegradable.
Degradable PEG hydrogels have been prepared by incorporating polymer segments based on poly(α-hydroxy acids) such as poly(lactic acid) and poly(glycolic acid) into the hydrogel. However, a problem with the incorporation of poly(α-hydroxy acid) segments into the PEG hydrogel is that the poly(α-hydroxy acid) segments can be very hydrophobic, which can be a significant factor in inciting major foreign body responses. A further problem with poly(α-hydroxy acid) segments is that when they degrade, they can generate a high local concentration of acids, which can incite an inflammatory response.
It would be desirable to provide a biodegradable polyether network polymer that addresses or ameliorates one or more disadvantages or shortcomings associated with existing materials and/or to at least provide a useful alternative to such materials.